The present invention is directed to a valve for controlling the flow of a high pressure fluid and, in particular, a valve for use in high cycle polymer operations.
The flow control of high pressure fluids is important in a variety of industries, including manufacturing, chemical production, refrigeration, plastics molding, automotive and medical applications. In the plastics molding industry, for example, fluids are often transferred at temperatures of several hundred degrees F and at pressures of several thousand psi.
In several methods of polymer production, described in International Publication No. WO 98/31521 (Pierick et. al.), International Publication No. WO 99/32544 (Anderson et. al.), and International Publication No. WO 98/08667 (Burnham, et. al.), each of which is hereby incorporated by reference herein, a gas blowing agent is mixed with a molten polymer to produce a mixture of gas and polymer. These processes may be used to produce, for example, injection molded, blow molded or extruded polymeric materials. Typically, a high pressure gas is injected and mixed with a molten polymer prior to the polymer being molded or extruded. Certain processes, e.g. injection molding, involve producing product cyclically, e.g., with many parts being made sequentially in the same mold. In such cases it may be preferred that the high pressure gas can be isolated from the polymer stream during the time the polymer is being transferred to a mold.
High pressure fluid valves used in cyclic operations are typically subjected to strenuous mechanically harsh conditions. It is one goal of the invention to provide a robust high-pressure valve for such use.
In one aspect, the invention provides a valve comprising a valve seat, a valve pin having a drive end and a sealing end, the valve pin mounted in the valve such that the sealing end is capable of mating with the valve seat, and a packing washer supporting the valve pin, the packing washer having a first end and a second end. An internal diameter of the packing washer varies between the first end and the second end.
In another aspect, the invention provides a valve comprising a valve seat positioned in a valve body, a valve pin positioned in the valve body, the valve pin having a sealing end and a drive end. The sealing end is capable of mating with the valve seat to prevent flow of fluid through the valve. A piston stem is positioned in a housing, the piston stem having a first end and a second end and capable of transferring axial force to the valve pin. The piston stem is uncoupled from the valve pin.
In another aspect, the invention provides a valve comprising a valve seat positioned in a valve body, a valve pin positioned in the valve body. The valve pin has a sealing end and a drive end. The sealing end is configured to mate with the valve seat to prevent flow of fluid through the valve. An energized seal surrounds a portion of the valve pin, and prevents flow of fluid past the seal.
In another aspect, the invention provides a valve comprising a valve seat, a valve pin capable of forming a fluid-tight seal with the valve seat, and a valve pin guide adjacent the valve seat. The valve pin guide has an internal diameter that is substantially the same as the outer diameter of the valve pin.
In another aspect, the invention provides a valve comprising a valve seat mounted in a valve body, and a valve pin having a sealing end and a drive end. The valve pin is slidably mounted in the valve body and axially movable between a first position wherein the sealing end is mated with the valve seat and a second position wherein fluid can flow through the valve. A valve guide is positioned adjacent to the valve seat, and an energized seal surrounds a portion of the valve pin. A piston stem moves the valve pin from the second position to the first position, and the piston stem is capable of transmitting axial force to the valve pin while permitting the axis of the piston stem to move independently of the axis of the valve pin.
In another aspect, the invention provides a system comprising any of the above valves in communication with a polymeric foam processing apparatus such as extrusion, injection molding, or blow molding apparatus.